03-15-2011
Quote:
Originally Posted by
omega666
and just to be clear again, when given 'w', the output of the string gets discarded or printed to stdout?
It depends on the caller's file descriptors and their flags.
Quote:
Originally Posted by popen opengroup documentation
The environment of the executed command shall be as if a child process were created within the
popen() call using the
fork() function, and the child invoked the
sh utility using the call:
execl(
shell path, "sh", "-c",
command, (char *)0) where
shell path is an unspecified pathname for the
sh utility.
So, as usual with fork/exec, the child will inherit all of its parents file descriptors that are not marked close-on-exec (FD_CLOEXEC). Additionally, there's the possibility of redirections in the command passed to "sh".
Regards,
Alister
Last edited by alister; 03-15-2011 at 05:52 AM..
10 More Discussions You Might Find Interesting
1. Programming
Hi
The following is my program to test popen()
routine. The purpose is to print some contents
of the corrent directory.
But in fact, the output is only one character
'a', which I believe is the first char of the file
"a.out".
So, can anybody tell me what is wrong about
this program?... (2 Replies)
Discussion started by: dell9
2 Replies
2. Programming
hai friends
I have written a tcp chat server in c.. I have designed a cgi program in c to control it... When i try to start the server from the cgi program, it is not starting. Why is that ? I have even tried giving the root ownership for all the programs.. Still its not.
I have used the... (1 Reply)
Discussion started by: collins
1 Replies
3. Programming
Hi there,
I'm facing a problem running the tar command with the popen function.
FILE* fp = popen("tar czf - textfile","r")
// output
this program should give the output to the stdout. I don't know if it is possible and which function like fprint() etc. should I use.
I suppose that I... (4 Replies)
Discussion started by: stef83
4 Replies
4. Programming
hi,
how to work with a background process without a controlling terminal to make use of popen or system call ?
when ever i use popen or system function call in foreground process, there is no problem with respect to that .. but when the same program is run as a background process without a... (7 Replies)
Discussion started by: matrixmadhan
7 Replies
5. Shell Programming and Scripting
Hello I'm writing a web server in python(obelisk-http.sourceforge.net)
and I'm having a greeat problem with POST method it like that
When someone make a POST request to the server it must open the executable(perl/python/.exe/elf) and send to the STANDART in (stdin) the request and get the... (2 Replies)
Discussion started by: sendai
2 Replies
6. Programming
Hi!
I'm trying to write a c program. The child process must transmit to the parent a file name and the parent must count the lines from the file and return te result to the child. Here is what i've done. It doesn't stop running, I guess. I'm sorry if it's an ugly code, i'm new at this stuff,... (2 Replies)
Discussion started by: alina89
2 Replies
7. UNIX for Advanced & Expert Users
Hi
I am trying to use popen function with wrtie option to give inputs to ftp command.
#include "stdio.h"
int main(int argv ,char *argc)
{
int size=0;
char *buf;
FILE *fp;
fp = popen("ftp","w");
while(getline(&buf,&size,stdin) != -1)
write(fp,buf);... (0 Replies)
Discussion started by: kumaran_5555
0 Replies
8. Programming
hi,
i am trying to use popen to run a grep process and check if the pattern exists in the file that i am searching in. i am getting segmentation fault when i try to execute the following code
char *cd;
char flag;
char hdr_flpsp;
char hdr_flpsp2;
FILE *fp;
printf ("program starts");... (1 Reply)
Discussion started by: sais
1 Replies
9. Programming
in man system it talks about SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.
Does this signal stuff also happen in popen command?
(even though man popen says nothing about signals)
also if I am not using wait(&status) and I am using waitpid(pid, NULL, 0)
how would... (1 Reply)
Discussion started by: omega666
1 Replies
10. Programming
Hello all,
I am reading a huge zip file in POPEN process and then writting that to a normal file which of 2GB. Now the process is failing when I looked for the cause someother process comming in after I read my file and it is deleting the zip. But in theory the popen command should read the... (5 Replies)
Discussion started by: arunkumar_mca
5 Replies
LEARN ABOUT DEBIAN
filter_create_fd
filter_create_fd(3) util/filter.h filter_create_fd(3)
NAME
filter_create_fd - Create a sub process and return the requested pipes
SYNOPSIS
#include <util/filter.h>
NEOERR *filter_create_fd(const char *cmd, int *fdin, int *fdout, int *fderr,
pid_t *pid);
ARGUMENTS
cmd -> the sub command to execute. Will be executed with
/bin/sh -c
fdin -> pointer to return the stdin pipe, or NULL if you don't
want the stdin pipe
fdout -> pointer to return the stdout pipe, or NULL if you don't
want the stdout pipe
fderr -> pointer to return the stderr pipe, or NULL if you don't
want the stderr pipe
DESCRIPTION
filter_create_fd and filter_create_fp are what popen
been: a mechanism to create sub processes and have pipes to all their input/output. The concept was taken from mutt, though python has
something similar with popen3/popen4. You control which pipes the function returns by the fdin/fdout/fderr arguments. A NULL value means
"don't create a pipe", a pointer to an int will cause the pipes to be created and the value of the file descriptor stored in the int. You
will have to close(2) the file descriptors yourself.
RETURN VALUE
fdin -> the stdin file descriptor of the sub process
fdout -> the stdout file descriptor of the sub process
fderr -> the stderr file descriptor of the sub process
pid -> the pid of the sub process
SEE ALSO
filter_wait(3), filter_create_fp(3), filter_create_fd
ClearSilver 12 July 2007 filter_create_fd(3)